In an inkjet printer, small ink droplets are jetted out from small nozzle holes provided at the inkjet head in accordance with print data, whereby an image is printed on a medium such as a sheet of paper. As an inkjet-type printer, one that forms a full color image using an inkjet head filled with ink of four colors, that is, cyan, magenta, yellow and black or six colors additionally including light cyan and light magenta, has been known. Recently, it has become a common practice to fabricate a wiring pattern, a color filter and the like by incorporating the inkjet head in a production system.
FIGS. 13 and 14 show a structure of the head element forming such an inkjet head. FIG. 13 is a perspective view showing a structure of a conventional head element, and FIG. 14 is a perspective view showing the structure of the head element cut along a section line S of FIG. 13.
A method of manufacturing a conventional head element will be described. A piezoelectric substrate 101 polarized along its depth direction is diced to form a plurality of trenches. The plurality of trenches will be ink chambers 104. On an inner wall of ink chamber 104, an electrode 105 is formed. Then, on the inner wall of ink chamber 104, an electrode protection film (not shown) of about 10 μm in thickness is formed to cover electrode 105. A rear end portion of ink chamber 104 (on the side opposite to the side to be in contact with a nozzle plate) is filled with a conductive material (not shown) to be conducted to electrode 105.
On piezoelectric substrate 101, a cover member 102 is attached to cover ink chambers 104. Cover member 102 has a common ink chamber 103 formed therein. Common ink chamber 103 is communicated with all the ink chambers 104 of piezoelectric substrate 101, and from common ink chamber 103, ink is supplied to each of ink chambers 104.
By adhering cover member 102 on piezoelectric substrate 101, a head element 100 is formed. When a voltage in accordance with the print data is applied to electrode 105, the wall portion of ink chamber 104 deforms. Consequently, the ink filled in ink chamber 104 is pressurized, and the ink is forced out from ink chamber 104.
The piezoelectric inkjet head as described above has a characteristic that it easily allows grayscale printing, as it is possible to control the pressure to be applied to the ink and hence the volume of ink droplets to be ejected, by controlling deformation of the piezoelectric body through voltage adjustment. When four colors of ink are used, four head elements 100 are integrated, and when six colors of ink are used, six head elements 100 are integrated, to form a head unit.
FIG. 15 is a perspective view of a conventional head unit having a plurality of head elements integrated. In a head unit 200 such as shown in FIG. 15, it is necessary to arrange each head element 100 relative to a head holding member 106 with high accuracy. When each head element 100 is not arranged at a prescribed position with respect to head holding member 106, the ink would not land on a prescribed spot of the recording paper, resulting in blurring and unsatisfactory image quality.
Positional deviation of head element 100 involves positional deviation in the direction of X, Y and Z axes as well as deviation in α, β and γ components representing rotation about these axes, as shown in FIG. 15. Unless positioning with respect to these six axes has sufficient accuracy, image quality would be unsatisfactory as described above.
In this regard, Japanese Patent Laying-Open No. H9-174833 describes an inkjet head in which a nozzle plate common to a plurality of head elements is adhered on a front surface and on a frame surface of the head elements. In the inkjet head, as the common nozzle plate is adhered, the ink landing accuracy is determined by the processing accuracy of the nozzle plate and the attitude of the plurality of inkjet heads integrated by the common nozzle, even if relative positions of the head elements are deviated from each other. Thus, it becomes possible to ensure high landing accuracy in a simple manner.
In a system for fabricating a wiring pattern, a color filter or the like incorporating the inkjet head, nozzle pitch of the inkjet head is adjusted to match pixel pitch or picture element pitch by arranging the inkjet head inclined by θ° relative to the printing direction.
Patent Document 1: Japanese Patent Laying-Open No. 9-174833